Wireless local area network (WLAN) systems that support operation in several bands are becoming more common A typical example is an Access point (AP) or a client device that can support operation in both the 2.4 GHz and 5 GHz bands, for example conforming to IEEE 812.11n communication standard. In some cases the AP or the client device may operate in both bands concurrently, while in other cases the client device may work at a given time slot in either one of the bands, non-concurrently. A concurrent dual band AP is more common than a concurrent dual band client. Usually a client device, even if it is dual band capable, would be configured to work in one of the two bands.
Historically, most WLAN devices worked in the 2.4 GHz band, which has only three 20 MHz channels available. As a result, the 2.4 GHz band is usually crowded with a variety of networks and interference sources, and high quality or service (QoS) level may not be maintained. The 5 GHz band, on the other hand, offers many more channels. Therefore, WLAN devices working in the 5 GHz band may be able to choose a substantially interference free channel and to guaranty a high level of QoS.
WLAN systems that support operation in several bands may offer flexibility in band and channel allocation. In some cases, for example, high QoS streams, like high definition (HD) video, would be carried in the 5 GHz band, while streams with less priority, like file transfer, would be carried in the 2.4 MHz band.
In some cases, for ease of operation, a concurrent dual band AP may use the same service set identifier (SSID) and/or basic service set identification (BSSID) in both bands. A non-concurrent dual band client may typically scan the spectrum before association and see the AP in both bands. It would then need to decide in which band to connect to the AP.
One of the practical problems with operation in multi-bands communication systems is how to manage the spectrum. There is currently no provision in the published WLAN standards for controlling the working band of a client device. While there is a provision for moving the entire basic service set (BSS) to a different channel using the dynamic frequency selection (DFS) procedure, this does not solve the problem of how to assign/move a specific client device to a different band.